-> (Type, -- closed type (rho)
UConSet) -- residual constraint set
-usgClos _ve ty ucs = (ty,ucs) -- dummy definition; no generalisation at all
+usgClos zz_ve ty ucs = (ty,ucs) -- dummy definition; no generalisation at all
-- hmm! what if it sets some uvars to 1 or omega?
-- (should it do substitution here, or return a substitution,